Protecting the MoSi2 healing particles for thermal barrier coatings using a sol-gel produced Al2O3 coating
A.L. Carabat (TU Delft - (OLD) MSE-1)
M.J. Meijerink (Student TU Delft)
JC Brouwer (TU Delft - (OLD) MSE-1)
E.M. Kelder (TU Delft - RST/Fundamental Aspects of Materials and Energy)
J. R. Van Ommen (TU Delft - ChemE/Product and Process Engineering)
S van der Zwaag (TU Delft - Novel Aerospace Materials)
W.G. Sloof (TU Delft - (OLD) MSE-1)
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Abstract
A successful sol-gel process to encapsulate molybdenum di-silicide MoSi2 particles with a closed and thermally stable Al2O3 layer using aluminium tri-sec-butoxide as a precursor is presented. The processing conditions such as precursor selection and temperature were optimized through analysing the interaction of the MoSi2 particles with the sol. The application of the sol-gel based coating was followed by calcining the coated particles at temperatures between 900 and 1200 °C in Ar. The shell composition and the mechanical stability of the microcapsule were analysed by means of X-ray diffraction, scanning electron microscopy and thermogravimetric analysis. Upon calcining at 1200 °C in Ar, the MoSi2 core remains intact as it is, covered by an α - alumina shell with a thickness of about 0.6 μm. The stability tests proved that the encapsulate particles are about five times more oxidation resistant than the uncoated MoSi2 particles.